U.S. Pat. No. 4,161,332, owned by the same company which owns the subject invention, is directed to a cylinderical stepped-thread configuration for pin and box joints for oil well tubing, a configuration which virtually eliminates the possibility of cross threading during make-up of pipe sections and results in shorter assembly time. This thread arrangement includes first and second pairs of interengaged sets of threads, one pair of threads being axially and radially spaced from the second pair.
U.S. Pat. Nos. 4,043,575 and 4,097,069 are directed to union-type couplings for riser pipes but are not considered optimally acceptable because they both utilize interrupted load carrying surfaces which cause an uneven load distribution around the circumference of the coupling, requiring a more massive coupling structure. Further, interrupted threads such as the ones in U.S. Pat. No. 4,097,069 are generally more expensive to manufacture than continuous threads because of the greater number of machining operations involved.
U.S. Pat. Nos. 3,827,728 and 4,068,865 are related to dog-type riser couplings which require a relatively long make-up time and massive coupling structure.
U.S. Pat. Nos. 4,093,281 and 4,124,230 utilize hydraulic cylinders to create a pre-tension on the box and pin portions and result in a relatively large coupling mass and structural complexity.